BRPI0907547B1 - MAGNETIC RESONANCE SYSTEM, SAFE BLOOD PRESSURE MONITOR FOR MRI, AND METHOD FOR MONITORING AN OBJECT IN A MAGNETIC FIELD - Google Patents

Abstract

"magnetic resonance system, safe blood pressure monitor for mri, and method for monitoring an object in a magnetic field" in magnetic resonance imaging (mri), powerful magnetic fields can interfere with, damage, cause premature failures in and attracting certain unsafe instruments of mr. The alliance of sensitive electromagnetic components is eliminated in favor of safe mr components such as piezoelectric ceramic components and bimetallic components. instruments, which previously had to be kept at a safe distance from the main magnet (12) - from, for example, more than 5 gauss lines - while the patient was being scanned, can now stay close to the patient without danger of damaging the instrument. instrument (40) and without danger to the patient, the medical team and the MRI device (10).

Description

“MAGNETIC RESONANCE SYSTEM, SECURE MONITOR OF

BLOOD PRESSURE FOR MRI, AND, METHOD FOR

MONITORING AN OBJECT IN A MAGNETIC FIELD ”

DESCRIPTION

The present application concerns the technique of creating diagnostic images. It finds application especially in safe accessories to be used with a scanner for magnetic resonance imaging that produces an intense magnetic field, and will be described here with special reference to it. It should be noted, however, that what is described in this application can also be used in more traditional environments, in the absence of intense magnetic fields, and is not limited to the application described above.

Magnetic resonance imaging (MRI) uses powerful magnetic fields to align the dipoles on a target in an imaging region. Often, rooms that house MRI magnets are magnetically shielded to prevent powerful magnetic fields from interfering with other magnetically sensitive devices. A potentially dangerous side effect of these powerful magnetic fields is the physical attraction they have on ferromagnetic materials in the vicinity. If any metal is placed in a region close to the magnet, the material can be propelled at great speed towards the magnet, with the risk of hurting people nearby, and damaging the magnet and the individual himself. Therefore, metallic objects, and / or objects that have metallic components, must be kept away from the magnet, at a safe distance, when it is operating in a field. Even if the magnetic attraction is not strong enough to physically move the device as a whole, in addition, the field can exert forces and torques that affect the operation of the device.

Another side effect is that the magnetic field can damage magnetically sensitive instruments and cause them to fail prematurely. Even at distances where physical attraction poses no danger, there is some magnetic field that can affect sensitive components. The failures can be temporary - and once removed from the field, the device starts to operate normally -, but the damage caused can be permanent, such as permanent deformation of the magnets, producing permanent failures. Magnetic forces in the movement of ferrous or electromagnetic parts can cause premature failures.

Automatic blood pressure monitors, for example, contain pumps that are typically powered by safe non-MRI components. Automatic and non-invasive blood pressure devices and gas monitors currently use centrifugal or peristaltic pumps driven by electromagnetic motors. The valves that operate on these devices are driven by electromagnetic solenoids. To be safe, these monitors must be kept at a safe distance from the magnet. If it is necessary to monitor a patient's blood pressure inside the MRI device, the long tubes or hoses must be extended from the pump and the valve portions of the monitor, to the cuff, mask or any other sensor installed on the patient , presenting a physical obstacle for the patient and the medical team with which they have to deal. Hoses have a negative impact on efficient flow as the monitor and patient are maneuvered around the MRI suite. In addition, the components inside the monitor are additionally the MRI suite and are affected by the magnetic field and tend to show premature failures. In the past, devices were assigned the “MR Conditional” rating when devices were labeled according to the maximum allowed exposure in the magnetic field. This can be translated as a safe distance from the MRI machine, with the constant field B _o .

To protect sensitive components from the magnetic field, ferromagnetic shields are sometimes used. Although these shields help to protect components from damage, they are not completely impenetrable magnetic fields and present additional risks related to physical attraction and, therefore, must be kept away. , at a safe distance. Although the shields help to alleviate premature failures of the sensitive components, the long hoses additionally continue to be extended from the patient in the MRI device to the monitor.

The present application provides a safe, new and improved device for MRI which seeks to resolve these and other problems.

According to one of the characteristics of the invention, an MRI system is provided. The main magnet generates a substantially uniform main magnetic field in a region of the image formation. A set of gradient coils imposes gradient magnetic fields on the main gradient magnetic fields of the main magnetic field, spatially encoding the main magnetic field. A set of radiofrequency induces magnetic resonance in selected dipoles from a region of an individual's image, and receives magnetic resonance signals from a region of the image formation. An automatic non-magnetic monitor screen measures and displays an individual parameter.

According to another feature, a safe blood pressure monitor is provided for MRI. A pressure cuff applies pressure to a patient's artery. A first transducer senses audible events within the artery under pressure. A peristaltic piezoelectric ceramic pump applies pressure to the pressure clamp. A first high voltage driver drives the piezoelectric pump. A second transducer senses the pressure applied to the pressure clamp. A first piezoelectric ceramic diaphragm valve releases pressure from the pressure clamp at a controlled linear rate. A second high-voltage actuator drives the first diaphragm piezoelectric valve. Pneumatic connections connect at least one pump and the pressure clamp. A control circuit controls at least one pump and the diaphragm valve. A power supply supplies power to at least a first and a second high voltage driver.

According to another characteristic, a method is provided to measure an individual's pressure in a magnetic field. A main magnetic field is generated by the main magnet of a magnetic resonance imaging device. A pressure clamp located in the main magnetic field is inflated by closing a first piezoelectric ceramic diaphragm valve, closing a second piezoelectric ceramic discharge diaphragm valve, and driving a piezoelectric ceramic pump. The pressure reading is made by releasing the air from the pressure clamp by opening the first valve and turning off the pump. After the first reading has been taken, the remaining air is released from the cuff by opening a second valve.

An advantage lies in the ability to monitor the patient's blood pressure in a high magnetic field environment, without using the long hoses.

Another advantage is the ability to monitor the gases administered in a high magnetic field environment without using the long hoses through which the piezoelectric ceramic pump draws the vacuum required for sampling the gases.

Another advantage is the increase in component life in high magnetic field environments.

Another advantage is the increase in mobility and access to the patient.

Another advantage lies in the reduction of ferromagnetic material in the vicinity of the MRI device.

Another advantage lies in increasing safety for the patient and the medical team.

Other additional advantages of the present invention will be seen by all those who have ordinary training in the technique, when reading and understanding the detailed descriptions that follow.

The invention can take its form through various components and arrangements of components and in various stages and arrangements of stages. The drawings are for the sole purpose of illustrating the preferred embodiments and are not to be construed as limitations of the invention.

Figure 1 is a diagrammatic illustration of a magnetic resonance imaging device with an MRI-safe medical monitor.

Figure 2 is a diagrammatic illustration of the blood pressure monitor according to the present application.

Figure 3 is an illustrative valve for the MRI-safe medical monitor.

Figure 4 is an illustrative pump for the MRI-safe monitor.

Figure 5 is an alternative embodiment of the MRI safety valve.

Figure 1 shows an MRI scanner 10. The MRI scanner 10 can be an open field system that includes a vertical main magnet assembly 12. The main magnet assembly 12 substantially produces a main magnetic field oriented along from a vertical axis to a region of the image. Although a vertical set of main magnet 12 is illustrated, partly to aid visualization, it should be understood that other magnet arrangements - such as the cylindrical and those with other configurations, are also contemplated. The main magnet 12 in an open system can have a field strength of about 2500 Gauss (0.25 T) up to 10,000 Gauss (1.0 T). A hole-type system can generate magnetic fields from 15,000 Gauss (1.5 T) to 70,000 Gauss (7.0 T), or more. Gauss line 5 is typically closer to the lower field strengths and further to the higher field strengths, but it can also vary with other factors, such as shielding and configuration.

A gradient coil assembly 14 produces gradients of the magnetic field in the region of the image formation to spatially encode the main magnetic field. It is preferable that the magnetic field gradient coil assembly 14 includes coil segments configured to produce the magnetic field gradient pulses in three orthogonal directions, typically the longitudinal or z, transverse or x and vertical or y directions.

A set of radio frequency coils 16 generates high frequency pulses to excite the resonance in the individual's dipoles. The set of radio frequency coils 16 also serves to detect the resonance signals that emanate from the region of the image. The radio frequency coil assembly 16 is a send / receive coil that forms an image of the entire region of the image, however, send / receive coils or dedicated local coils are also contemplated.

Gradient pulse amplifiers 18 provide controlled electrical currents to the magnetic field gradient set 14 to produce selected magnetic field gradients. A radio frequency transmitter 20, preferably digital, applies radio frequency pulses or pulse packets to the radio frequency array 16 to excite the selected resonance. A radio frequency receiver 22 is coupled to the coil set 16 or to separate coils to receive and demodulate the induced resonance signals.

To acquire an individual's MRI data, the individual is placed within an image-forming region. A sequence controller 24 communicates with gradient amplifiers 18 and radiofrequency transmitter 20 to supplement optical manipulation in the region of interest. The sequence controller 24 produces, for example, a selected steady state that is repeated by echo, or other resonance sequences; spatially encodes these resonances; manipulates or corrupts resonances; or alternatively, it generates the magnetic resonance signals selected and characteristic of the individual. The signals generated by the resonance are detected by the RF coil set 16 - or by a local coil (not shown) -; communicated to the radio frequency receiver 22; demodulated and stored in the K space of a memory 26. The image formation data is reconstructed by a reconstruction processor 28 to produce representations of the images that are stored in an image memory 30. In a suitable embodiment, the processor of reconstruction 28 performs an inverse reconstruction, using a Fourier transformation.

The representation (s) of the resulting image (s) is (are) processed by a video processor 32 and displayed on a user interface 34 provided with a human-readable display. Interface 34 is preferably a personal computer or a workstation. Instead of producing a video image, the representation of the image can be processed by a print driver and printed, transmitted to a computer network, or over the internet, or in any other similar way. Preferably, the user interface 34, additionally allows the radiologist, or another operator, to communicate with the sequence controller 24 to select the sequences of the image formation by magnetic resonance, modify the image sequences, perform the image formation, and so on.

A portable monitor 40 is located with the patient in a magnetic field. Monitor 40, in the illustrated embodiment, is a blood pressure monitor and is connected to a typical pressure cuff 42 by means of at least one air hose 44. A two-hose system is described below. It should be understood, however, that any parameters can be measured, and that the present application is not necessarily limited specifically to blood pressure monitors. When measuring blood pressure, cuff 42 is inflated by exerting measurable pressure on the patient, typically on the patient's biceps. The cuff 42 is inflated so that the pressure of the cuff 42 is increased to a pressure above the patient's systolic blood pressure. This temporarily interrupts blood flow along the brachial artery. Air is then allowed to bleed out of the cuff at a constant rate. When blood begins to flow in the brachial artery, that is, when cuff 42, or another sensor in the arm detects the pulse, monitor 40 records the pressure value as the patient's systolic pressure. Air continues to bleed out of cuff 42 until the cuff can no longer detect the pulse and the pressure value at which the pulse is lost is recorded as that of the patient's diastolic pressure.

In Figure 2, the blood pressure monitor 40 is shown in greater detail, including the components that make the measurements described above possible. To increase the pressure in cuff 42 a pump 26 • x draws air from the atmosphere and pumps it to cuff 42. As cuff 42 inflates the system is closed so that the pressure increases inside cuff 42. In In the embodiment shown in Figure 3, the pump 46 is a piezoelectric pump, and, more specifically, it is a peristaltic driven ceramic piezoelectric pump, although other types of piezoelectric pumps can also be contemplated. A piezoelectric element 46a expands and contracts in the direction indicated by the arrow. When the piezoelectric element is activated, it deflects a flexible diaphragm 46b. When the diaphragm 46b is deflected, it reduces the volume in the pump chamber 46c, pumping the fluid from the chamber through a check valve outlet 46d. When the piezoelectric element 46a relaxes, the volume of the pump chamber 46c increases and draws the fluid through the inlet valve 46e. Both check valves 46d and 46e are pressure-operated one-way valves that prevent reverse flow through the pump chamber 46c. The piezoelectric element 46a of the pump 46 is driven by an associated high voltage driver 48. The driver 48 is controlled by a monitor controller 50.

To feel if blood is flowing in the brachial artery, a first transducer 52 is placed on, or adjacent to, cuff 42. When blood begins to flow, it is accompanied by a characteristic sound (first Korptkoff sound) that is produced by the flow turbulent flow of blood and detected by transducer 52. A second transducer 54 measures the pressure of the cuff 42. After the pump 46 has inflated the cuff 42 to press, air is bled out of the cuff 42 by means of a linear valve 56. embodiment shown in Figure 4, linear valve 56 is a piezoelectric ceramic diaphragm valve; a piezoelectric element 56a expands and contracts in the manner indicated by the arrows. When the piezoelectric element expands, it forces the valve element 56b to come into contact with a region of the valve 56c that seals the valve 56. When the piezoelectric element 56a relaxes, the valve 56 opens and the fluid can flow through it. Optionally an operable pilot piezoelectric valve can be used. The linear valve 56 has its own high voltage driver 58 which is also controlled by the monitor controller 50. Optionally the linear valve can be driven by a metallic element 56a, in which the measured electrical currents create heat and cause a known deflection. The valve then allows a known flow to pass. This type is also non-magnetic, and an additional high voltage driver would not be necessary. When the pressure in cuff 42 is between the systolic and diastolic pressures of the patient, the blood flow will be turbulent, as the blood pressure jumps above the cuff pressure and falls back below the cuff pressure with the beats of the patient's heart. Once the pressure of cuff 42 is between the systolic and diastolic pressures, the first transducer 52 will be able to detect the turbulent flow of blood. Once the pressure drops below the systolic pressure, the flow through the brachial artery will no longer be turbulent, since the artery is no longer constricted. No additional sounds are detected. When the first transducer 52 can no longer detect any sounds, the pressure reported by the second transducer 54, in which this occurs, is recorded as the diastolic pressure.

Once the diastolic pressure has been recorded, a discharge valve 60 opens and releases the remaining air in the cuff 42 into the atmosphere. In one embodiment, like the linear valve 56, the discharge valve 60 is a piezoelectric ceramic diaphragm valve. Likewise, the discharge valve 60 is driven by its own high voltage actuator 62. Actuators 48, 58, 62 are all controlled so that the above detailed process is performed by monitor controller 50. During the process of inflating the clamp 42, pump 46 is switched on, and both linear valve 56 and discharge valve 60 are closed. During blood pressure measurement, pump 46 is turned off, linear valve 56 is opened and the discharge valve 60 remains closed. Once the diastolic pressure has been read - and during periods of non-use - the pump 46 is turned off, and both valves 56 and 60 are opened. If monitor 40 fails to read, controller 50 can immediately start the process again. Optionally, the discharge valve can be driven by a bimetallic element, which converts electricity to heat, to move the valve actuation without the need for an additional high voltage actuator.

As previously mentioned, the process is controlled by a monitor controller 50. Preferably, the user can interface with the monitor controller 50, via a user interface 64. The user can command a reading at a specified time, or a set of periodic readings, and analyze the recent pressure readings, stored in the memory of monitor 66. Optionally, transceiver 68 is included in monitor 40 so that controller 50 can transmit readings to a remote workstation, and example of a serial station, an operator, a nurse or a monitor 70 processing unit. An adequate power source 72, such as a battery, or an AC adapter, or a system that captures the power of the MR system, supplies power to the monitor 40. Preferably the monitor 40 is equipped with a rechargeable battery, like the non-magnetic lithium-ion battery, which can be plugged into a wall outlet when inactive, but wireless when in use.

When using piezoelectric ceramic elements, the electromagnetically sensitive components are absent from the monitor 40. In this way, the classification “MR Segura” can be assigned and the patient can be followed in the field of the MR device, eliminating the need for extensive cables and tubes leading from monitor 40 to the patient. The piezoelectric design is also applicable to wireless, portable, table and pedestal blood pressure monitors in the same way, but specifically to monitors that can move with the patient into the hole of the MR device. Optionally, the monitor is shielded with a shield against electromagnetic interference 74 to prevent monitor 40 from having a negative impact on acquisition or image quality. In addition, controller 50 and memory 66 are also shielded against magnetic fields.

In another embodiment, a gas monitor, like a monitor capable of measuring the final normal exhalation of CO ₂ and which supplies anesthetic gases, is configured with piezoelectric ceramic pumps and valves for use in MRI systems. In gas monitors a breathing mask is placed over the patient's mouth. A piezoelectric peristaltic pump pumps gas from the mask and an associated exhaust line. Piezoelectric valves are operated to move a measured volume of exhaust gas into an analysis chamber, trap the gas in the chamber during the analysis time and exhaust the gas after analysis.

Other types of safe magnetic field pumps and valves are additionally contemplated. As shown in Figure 5, a bimetallic element 80 is heated by a heater 82 and allowed to cool, to cause its displacement to a striker 84 in the direction indicated by the arrows. The striker 84 flexes a diaphragm 86 and causes it to drive the valve region 88 between the open and closed positions. Similarly, heating and cooling of the bimetallic element 89 can pump the diaphragm of the peristaltic pump. Other types of safe MR safe valves and pumps are additionally contemplated.

The invention has been described with reference to the preferred embodiments. Modifications and changes to third parties may occur when they read and understand the detailed preceding descriptions. These modifications and alterations are intended to be included in the interpretation of the invention, insofar as they fall within the scope of the appended claims or those equivalent to them.

Claims (15)

1. Magnetic resonance system, comprising: a main magnet (12) to generate a substantially uniform main magnetic field in an examination region; a set of gradient coils (14) to impose gradient magnetic fields on the main magnetic field in the examination region, spatially encoding the main magnetic field; a radiofrequency set (16) to induce magnetic resonance in selected dipoles of an individual in an examination region and receive the magnetic resonance; and an automatic non-magnetic monitor (40) arranged, at least partially, in the examination region to measure and display at least one physiological parameter of the individual; and characterized by the fact that the automatic non-magnetic monitor (40) includes at least one of a piezoelectric ceramic peristaltic pump (46) and a piezoelectric ceramic diaphragm valve (56). 2. Magnetic resonance system according to claim 1, characterized by the fact that it additionally includes: high voltage driver (48) for the piezoelectric pump (46) arranged in the examination region. 3. Magnetic resonance imaging system according to any one of claims 1 and 2, characterized in that it additionally includes: high voltage actuator (58) for the piezoelectric diaphragm valve (56) arranged in the examination region. Magnetic resonance imaging system according to any one of claims 1 to 3, characterized in that the non-magnetic monitor (40) includes one of a blood pressure monitor (40) and a gas analysis monitor. Petition 870180160176, of 12/07/2018, p. 7/14 5. Magnetic resonance imaging system according to claim 4, characterized in that the monitor (40) includes a blood pressure monitor, the blood pressure monitor including: a piezoelectric ceramic peristaltic pump (46) arranged in the examination region; at least one piezoelectric ceramic diaphragm valve (56) arranged in the examination region; a controller (50) for controlling the high voltage actuators (48.58) to drive the pump (46) and the valve (56); a memory (66) for storing at least blood pressure readings and the time taken to measure them; and an electromagnetically compatible housing (74) around the controller (50) and memory (66) to shield against radiation emissions. 6. Magnetic resonance imaging system according to any one of claims 1 to 5, characterized in that the monitor (40) additionally includes: at least one valve or pump operated by a bimetallic element. 7. Magnetic resonance system according to any one of claims 1 to 6, characterized by the fact that the main magnet generates a magnetic field of at least 2,500 Gauss (0.25 T) in the examination region. 8. Safe MRI blood pressure monitor for use with the MRI system as defined in claim 1, comprising: a pressure cuff (42) for applying pressure to a patient's artery; a first transducer (52) for sensing audible events Petition 870180160176, of 12/07/2018, p. 8/14 inside the artery under pressure; a second transducer (54) for sensing the pressure applied to the pressure clamp (42); characterized by the fact that a piezoelectric ceramic peristaltic pump (46) is configured to pressurize the pressure clamp (42); a first high voltage driver (48) is configured to drive the piezoelectric pump (46); a first piezoelectric ceramic diaphragm valve (56) is configured to release pressure from the pressure clamp at a controlled linear rate; a second high voltage driver (58) is configured to drive the first diaphragm piezoelectric valve (56); pneumatic connections (44) are configured to connect at least one pump (46) and the second pressure clamp (42); control circuits (50) are configured to control at least one pump (46) and the diaphragm valve (56); and power supply (72) is configured to supply power to at least a first and a second high voltage driver (48.58) and to the control circuits (50). 9. Safe MRI blood pressure monitor according to claim 8, characterized in that it additionally includes: a housing against electromagnetic interference (74) around at least the piezoelectric pump (46) and the valve (56), shielding the housing (74) against radiation emissions. 10. Safe MRI blood pressure monitor according to any of claims 8 and 9, characterized in that the first piezoelectric valve (56) is a linear relief valve. 11. Safe MRI blood pressure monitor according to Petition 870180160176, of 12/07/2018, p. 9/14 with claim 10, characterized by the fact that it additionally includes: a second piezoelectric diaphragm valve (60) that functions as a discharge valve to release pressure from the monitor; and a third high voltage driver (62) for driving the second diaphragm piezoelectric valve (60). 12. Safe MRI blood pressure monitor according to claim 11, characterized by the fact that both valves are bimetallic driven devices. 13. Safe MRI blood pressure monitor according to any of claims 8 to 12, characterized in that the blood pressure monitor (40) is partially arranged in the examination region. 14. Method for monitoring an object in a magnetic field, comprising: generation of a substantially uniform magnetic field by means of a main magnet (12) of an MRI device in an examination region; imposition of gradient magnetic fields on main magnetic fields in the examination region and spatially encoding the main magnetic field with a system of gradient coils (24); induction of magnetic resonance in selected dipoles of an individual in the examination region and receiving the magnetic resonance with a set of RF (16); and measuring and displaying at least one physiological parameter of the individual with an automatic non-magnetic monitor (40) at least partially arranged in the examination region; and characterized by the fact that the automatic non-magnetic monitor (40) includes at least one piezoelectric ceramic diaphragm valve (56, 60) and a piezoelectric ceramic peristaltic pump (46). Petition 870180160176, of 12/07/2018, p. 10/14 A method according to claim 14, comprising; the automatic non-magnetic monitor (40) includes a blood pressure monitor, the blood pressure monitor including: a pressure cuff (42) for applying pressure to a patient's artery; a first transducer (52) for sensing audible events within the artery under pressure; a second transducer (54) for sensing the pressure applied to the pressure clamp (42); characterized by the fact that a peristaltic piezoelectric ceramic pump (46) pressurizes the pressure clamp (42); a first high voltage driver (48) drives the piezoelectric pump (46); a first piezoelectric ceramic diaphragm valve (56) releases pressure from the pressure clamp at a controlled linear rate; a second high voltage driver (58) drives the first diaphragm piezoelectric valve (56); pneumatic connections (44) connect at least the pump (46) and the second pressure clamp (42); control circuits (50) control at least one pump (46) and the diaphragm valve (56); and power supply (72) takes power to at least a first and a second high voltage driver (48, 58) and to the control circuits (50).